The National Bus and Rail Union has accused Minister for Transport Leo Varadkar of "demonising" Iarnród Éireann.
NBRU General Secretary Dermot O'Leary was speaking as he arrived for a Labour Court hearing on cost reduction proposals, which include pay cuts up until 2017.
Mr O'Leary said his members were not prepared to accept pay cuts at a time when the minister was demonising and disparaging the rail service.
He said it would be quite difficult to ask members to contribute from their pay packets to a railway service which, according to the minister, had no future.
He noted that operating costs at Iarnród Éireann had been reduced by €74m since 2008 and that 2,500 staff had left the company over the past ten years.
SIPTU Assistant Organiser Paul Cullen said if the current proposals were implemented, including the pay cuts lasting until 2017, workers would have had pay restraint for nine years.
Asked about the prospect of industrial action in the dispute, Mr Cullen said he would not rule it in or out at the moment.
Iarnród Éireann management declined to comment as they arrived at the Labour Court.
However, the company has previously stated that delayed implementation of the cuts is costing it €100,000 per week.
Unions have previously rejected proposals brokered by the Labour Relations Commission.